This will be the last upgrade for a while though.
.[/QUOTE]
Is that what you told your wife??
15 minute subs is probably good anyway. If you have dark skies then I would go as long as tracking and cloud allows. 15 minutes is more to invest if its cloudy and you may wind up with less data than if you used 10 minutes.
Optimum exposure length is an interesting topic. SBIG has a calculator on their site for that as I recall.
Although it may not be 100% accurate for you as your read noise etc may be a tad different.
Greg.